The production of increasingly finer structures with the aid of lithographic methods in the manufacture of semiconductor components often involves light having an increasingly short wavelength. If light in the extreme ultraviolet (EUV) wavelength range is used, e.g. at wavelengths of between about 5 nm and 20 nm, it is generally no longer possible to use lens-type elements in a transmission mode, but rather illumination and projection objectives constructed of mirror elements each having reflective coatings adapted to the respective working wavelength are used. In contrast to mirrors in the visible and ultraviolet wavelength ranges, theoretically only a maximum reflectivity of less than 80% can generally be achieved per mirror. Since EUV projective devices usually include a plurality of mirrors, it is desirable for each of them to have relatively high reflectivity to help ensure sufficiently high overall reflectivity.
U.S. Pat. No. 6,927,901 discloses an EUV projection objective that includes a plurality of imaging mirrors between the object plane and the image plane, which define an optical axis and include reflective coatings. At least one of the mirrors has a graded reflective coating with a coating thickness profile that is rotationally symmetrical with respect to a coating axis, wherein the coating axis is eccentrically arranged with respect to the optical axis in order to achieve higher overall transmission of the projection objective.